<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
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    <title>Document</title>
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<body>
<script>
  function recursion(n) {
      if(n < 0){
          return '输入的数字不能小于0';
      }else if (n == 0){
          return 0;
      }else if (n == 1){
          return 1;
      }else if (n > 1){
          return recursion(n - 1) + recursion(n - 2);
      }
  }
  console.log(recursion(10));
</script>    
</body>
</html>